You will not be able to see the 10 year old while you are supervising in Nemo's Reef. However, we let our 6 year old do the Mickey Slide while I was in the Reef with his little sister (and may have even let him when he was 4, but I don't totally remember) as we trusted him to just stay there and not go into the actual pool. The slide doesn't go into the pool. In Shmoo's first photo above, those stairs at the top go to the pool deck, with Mickeys slide just to the right. However, the entrance and exit to the slide are around a corner - you have to walk out and around a bit - and you can't see the kids in the slide even from that angle. The Mickey pool is straight ahead from those stairs, with maybe 4 rows of chairs in between the stairs and pool.